Developing highly efficient oxygen evolution reaction (OER) catalysts and understanding their activity are pivotal for electrochemical conversion technologies. Here, we report NiFe Prussian blue analogue (PBA) as a promising electrocatalyst for OER in alkaline conditions. This material has an impressively low overpotential of 258 mV that reaches a current density of 10 mA cm. Post-mortem characterization showed that the as-prepared catalyst is entirely transformed into amorphous nickel hydroxide after the electrochemical treatment, and Ni(OH) acts as the active species. Operando X-ray spectroscopic studies further found that this in situ generated Ni(OH) displays an unique feature that allows deprotonation under applied potential creating NiOOH that contains Ni ions. The deprotonation reaction is reversible and potential-dependent, i.e., the amount of Ni increases with increasing applied potential. Theoretical calculations were used to show that the role of Ni is to trigger oxidized oxygen ions as electrophilic centers with the subsequent activation of anion redox reactions for OER.

Operando XAS combined with DFT calculations allows us to draw a phase diagram of the surface chemical state as a function of applied potential, showing hydroxyl filling process and potential-dependent deprotonation process.

While inheriting the exceptional merits of single atom catalysts, diatomic site catalysts (DASCs) utilize two adjacent atomic metal species for their complementary functionalities and synergistic actions. Herein, a DASC consisting of nickel-iron hetero-diatomic pairs anchored on nitrogen-doped graphene is synthesized. It exhibits extraordinary electrocatalytic activities and stability for both CO2 reduction reaction (CO2RR) and oxygen evolution reaction (OER). Furthermore, the rechargeable Zn-CO2 battery equipped with such bifunctional catalyst shows high Faradaic efficiency and outstanding rechargeability. The in-depth experimental and theoretical analyses reveal the orbital coupling between the catalytic iron center and the adjacent nickel atom, which leads to alteration in orbital energy level, unique electronic states, higher oxidation state of iron, and weakened binding strength to the reaction intermediates, thus boosted CO2RR and OER performance. This work provides critical insights to rational design, working mechanism, and application of hetero-DASCs.

Unravelling the intrinsic mechanism of electrocatalytic oxygen evolution reaction (OER) by use of heterogeneous catalysts is highly desirable to develop related energy conversion technologies. Albeit dynamic self‐reconstruction of the catalysts during OER is extensively observed, it is still highly challenging to operando probe the reconstruction and precisely identify the true catalytically active components. Here, a new class of OER precatalyst, cobalt oxychloride (Co2(OH)3Cl) with unique features that allow a gradual phase reconstruction during OER due to the etching of lattice anion is demonstrated. The reconstruction continuously boosts OER activities. The reconstruction‐derived component delivers remarkable performance in both alkaline and neutral electrolytes. Operando synchrotron radiation‐based X‐ray spectroscopic characterization together with density functional theory calculations discloses that the etching of lattice Cl− serves as the key to trigger the reconstruction and the boosted catalytic performance roots in the atomic‐level coordinatively unsaturated sites (CUS). This work establishes fundamental understanding on the OER mechanism associated with self‐reconstruction of heterogeneous catalysts.

p-d Conjugated coordination polymers (CCPs) have attracted muchattention for various applications,although the chemical states and structures of many CCPs are still blurry. Now,aone-dimensional (1D) p-d conjugated coordination polymer for high performance sodium-ion batteries is presented. The chemical states of the obtained coordination polymer are clearly revealed. The electrochemical process undergoes at hree-electron reaction and the structure transforms from C=Nd ouble bonds and Ni II to CÀNs ingle bonds and Ni I ,r espectively.Our unintentional experiments provided visual confirmation of Ni I .T he existence of Ni I was further corroborated by its X-raya bsorption near-edge structure (XANES) and its catalytic activity in Negishi cross-coupling.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Operando X-ray absorption spectroscopy (XAS) technique unravels that the CoFe nanoparticles in a new type of lanthana-anchored CoFe catalyst are nearly transformed into unique (Co/Fe)O(OH) under the electrochemical condition, as real active species for oxygen evolution reaction.

Copper-based materials can reliably convert carbon dioxide into multi-carbon products but they suffer from poor activity and product selectivity. The atomic structure-activity relationship of electrocatalysts for the selectivity is controversial due to the lacking of systemic multiple dimensions for operando condition study. Herein, we synthesized high-performance CO2RR catalyst comprising of CuO clusters supported on N-doped carbon nanosheets, which exhibited high C2+ products Faradaic efficiency of 73% including decent ethanol selectivity of 51% with a partial current density of 14.4 mA/cm−2 at −1.1 V vs. RHE. We evidenced catalyst restructuring and tracked the variation of the active states under reaction conditions, presenting the atomic structure-activity relationship of this catalyst. Operando XAS, XANES simulations and Quasi-in-situ XPS analyses identified a reversible potential-dependent transformation from dispersed CuO clusters to Cu2-CuN3 clusters which are the optimal sites. This cluster can’t exist without the applied potential. The N-doping dispersed the reduced Cun clusters uniformly and maintained excellent stability and high activity with adjusting the charge distribution between the Cu atoms and N-doped carbon interface. By combining Operando FTIR and DFT calculations, it was recognized that the Cu2-CuN3 clusters displayed charge-asymmetric sites which were intensified by CH3* adsorbing, beneficial to the formation of the high-efficiency asymmetric ethanol.

Precisely tailoring the electronic structures of electrocatalysts to achieve an optimum hydroxide binding energy (OHBE) is vital to the alkaline hydrogen oxidation reaction (HOR). As a promising alternative to the Pt-group metals, considerable efforts have been devoted to exploring highly efficient Ni-based catalysts for alkaline HOR. However, their performances still lack practical competitiveness. Herein, based on insights from the molecular orbital theory and the Hammer–Nørskov d-band model, we propose an ingenious surface oxygen insertion strategy to precisely tailor the electronic structures of Ni electrocatalysts, simultaneously increasing the degree of energy-level alignment between the adsorbed hydroxide (*OH) states and surface Ni d-band and decreasing the degree of anti-bonding filling, which leads to an optimal OHBE. Through the pyrolysis procedure mediated by a metal–organic framework at a low temperature under a reducing atmosphere, the obtained oxygen-inserted two atomic-layer Ni shell-modified Ni metal core nanoparticle (Ni@Oi-Ni) exhibits a remarkable alkaline HOR performance with a record mass activity of 85.63 mA mg–1, which is 40-fold higher than that of the freshly synthesized Ni catalyst. Combining CO stripping experiments with ab initio calculations, we further reveal a linear relationship between the OHBE and the content of inserted oxygen, which thus results in a volcano-type correlation between the OH binding strength and alkaline HOR activity. This work indicates that the oxygen insertion into the top-surface layers is an efficient strategy to regulate the coordination environment and electronic structure of Ni catalysts and identifies the dominate role of OH binding strength in alkaline HOR.